Secure File Sharing System

Skills: Go(Golang), Symmetric and Assymetric Cryptography, Signatures, Slow Hashing, Security, Unit Testing

This project was completed as a part of CS161 - Computer Security class with my project partner - Sanzhar Abatov. The entire code was writted from scratch in Go with over 3000 lines and was fully tested using custom unit tests.

We have developed a file system similar to Google Docs, where users can store, edit, invite other users, accept invitations to collaborate and revoke file rights. The whole system is based on one insecure database and one small secure database only for public keys (Trusted Computer Base). The goal was to implement a fully secure system despite the two main adversaries that can edit or delete anything on the insecure database with the main objectives of keeping the file contents, file names (and their length) and user structs fully secure. There was also a requirement for the transaction’s bandwith to not scale with number of users and files which was achieved through using linked-list like structure of saving files.

In order to achieve this, we have used RSA assymetric encryption in combination with symmetric keys (El Gamal scheme modification), cryptographic MACs, slow hashing schemes like Argon2Key, digital signatures and other cryptographical algorithms. For the system itself, we have used structs for each component placed on the database in the Marshalled form.

Here is one of sample tests we have used to assess our system

Describe("Basic Tests", func() {

		Specify("Basic Test: Testing InitUser/GetUser on a single user.", func() {
			userlib.DebugMsg("Initializing user Alice.")
			alice, err = client.InitUser("alice", defaultPassword)
			Expect(err).To(BeNil())

			userlib.DebugMsg("Initializing user without password.")
			bob, err = client.InitUser("gyat", "") // can initialize the user with empty password
			Expect(err).To(BeNil())

			userlib.DebugMsg("Initializing user Alice with already used username and different password.")
			alice, err = client.InitUser("alice", wrongPassword) // can not initialize the user with the same username
			Expect(err).ToNot(BeNil())

			userlib.DebugMsg("Initializing user Alice.")
			alice, err = client.InitUser("alice", defaultPassword) // also can not initialize
			Expect(err).ToNot(BeNil())

			userlib.DebugMsg("Getting user Alice.")
			aliceLaptop, err = client.GetUser("alice", defaultPassword)
			Expect(err).To(BeNil())

			userlib.DebugMsg("Getting unexistant user.")
			aliceDesktop, err = client.GetUser("bruh", defaultPassword) // can not get unexistant user
			Expect(err).ToNot(BeNil())

		})